LATERAL VIBRATION ANALYSIS OF CONTINUOUS BRIDGES UTILIZING EQUAL DIS-PLACEMENT RULE

Abstract

THE EQUAL DISPLACEMENT RULE IS WELL-KNOWN AS AN EMPIRICAL RULE FOR THE ASSESSMENT OF THE NON-LINEAR BEHAVIOUR OF STRUCTURES SUBJECTED TO SEISMIC EXCITATION. THE APPLICATION OF EQUAL DISPLACEMENT RULE SIMPLIFIES THE EVALUATION OF LATERAL DISPLACEMENT DEMAND OF MANY CONTINUOUS BRIDGES, AND THUS PROVIDES THE BASIS FOR THEIR DISPLACEMENT-BASED SEISMIC DESIGN. HOWEVER, THE APPLICATION CONDITIONS OF EQUAL DISPLACEMENT RULE IN MULTI-DEGREE-OF-FREEDOM (MDOF) BRIDGE SYSTEMS REQUIRE MORE INVESTIGATIONS. IN THIS PAPER, THE APPLICATION CONDITIONS OF EQUAL DISPLACEMENT RULE OF SINGLE-DEGREE-OF-FREEDOM (SDOF) ARE INTRODUCED. A COMPREHENSIVE STATISTICAL ANALYSIS OF THE RATIO OF MAXIMUM INELASTIC DISPLACEMENT TO MAXIMUM ELASTIC DISPLACEMENT FOR TYPICAL CONTINUOUS BRIDGES IS PERFORMED, AND EQUAL DISPLACEMENT RULE OF SDOF IS EXTRAPOLATED TO MDOF SYSTEM. AS FOR THE BRIDGES WITH LONG PERIODS, THE APPLICATION OF EQUAL DISPLACEMENT RULE ON MDOF SYSTEM IS FURTHER SIMPLIFIED. IT IS CONCLUDED THAT EQUAL DISPLACEMENT RULE OF MDOF IS APPLICABLE TO CONTINUOUS BRIDGES WHEN THE PERIODS OF THE MAIN MODES ARE NOT LESS THAN THE LIMITING PERIOD, WHICH IS RELATED TO THE LEVEL OF INELASTIC DEFORMATION OF THE BRIDGE SUBJECTED TO EARTHQUAKES. FURTHERMORE, THE ACCORDING LIMITING PERIOD CAN BE SIMPLIFIED TO A FIXED VALUE BASED ON THE DISPLACEMENT CAPACITY OF PIERS.